1 Field of the Invention
This invention relates to a method of repairing the moisture barrier separating a paper machine dryer drum from the dryer journal. Such processes of this type, generally, involve substantially filling the air cavity between the dryer steam intake pipe and the dryer journal with a flowable moisture barrier.
2 Description of the Prior Art
In conventional paper making machines several large dryer drums or heated cylinders are located near the end of the paper machine. The dryer drums are conventionally filled with steam at approximately 200 to 300 F degrees under pressure. The dryer drums contact both sides of the paper web and reduce the paper""s water content to approximately 5%. The dryer drums are typically 5 feet wide or wider and typically weigh in excess of 2 tons. Each drum end is supported by a journal head. Each journal head is further supported by a journal assembly at each end.
FIG. 1 is a cross-sectional drawing of a prior art journal assembly 2. The journal assembly 2 acts as an axle to rotate the dryer drum (not shown) about a central axis. The journal assembly 2 typically has a hollow, annular main journal body 3, hereinafter referred to as the journal. The journal 3 is supported by and rotated via journal bearings 4. The bearings 4 are typically located in a housing. U.S. Pat. No. 4, 716, 661 by Asman is an exemplary reference of a hollow, annular journal for a paper machine dryer. Typically the dryer drum steam intake pipe 12 is placed into the hollow portion of the journal 3 as shown in FIG. 1. Typically, steam enters into the dryer drum in the direction of arrow A. Typically a steam condensate pipe 8 is located internal to the steam intake pipe 12. In such cases, the steam condensate exits the dryer drum in the direction of arrow B.
A thin annular cavity 16 separates the dryer steam intake pipe 12 from the journal 3. This air cavity, primarily, serves as a heat insulator between the dryer steam intake pipe 12 and the journal 3. The cavity eliminates most heat transfer from the steam intake pipe 12 to the journal bearings 4.
Conventionally a journal moisture barrier 20 is used to prevent steam from leaving the dryer drum and entering the cavity 16. Typically, the journal moisture barrier 20 is an annular flange with a polymeric coating-based material or other moisture barrier, such as a rubber gasket. The journal moisture barrier is typically secured to the journal 3 by bolts 21 so that the polymeric coating touches the journal 3. However, conventional journal moisture barriers 20 often fail to withstand the high temperatures of the dryer steam that can reach as high as 390xc2x0 F. Frequently, the journal moisture barrier 20 breaks down or develops a leak that allows moisture from the dryer drum to enter the cavity 16. As high temperature moisture enters the cavity 16 unacceptable amounts of heat are transferred through the journal 3 to the journal bearings 4. High temperature moisture leaks adversely impacts the journal 3 and the bearings 4. The moisture can cause the journal""s 3 metal surface too pit and can breakdown the bearing""s 4 lubrication (not shown) and lubrication system (not shown). Typically a leak in the journal moisture barrier 20 is detected by moisture exiting the cavity 16 via an opening 14, such a weep hole.
It is known to replace conventional journal moisture barriers 20 when they break down or leak. However, this requires many man-hours of labor and downtime for the entire paper machine to replace one moisture barrier, which ultimately leads to reduced paper production. An exemplary description of a conventional replacement or repair method is described in U.S. Pat. No. 4, 716, 661, column 4, lines 55-70. A typical paper machine includes many dryer journal moisture barriers 20 so the potential maintenance cost and paper machine downtime is great. Also, simply replacing one conventional journal moisture barrier 20 with another does not eliminate future replacements. Therefore, a more advantageous repair method for damaged journal moisture barriers 20 is highly desirable.
It is apparent from the above that there exists a need in the art for a method to quickly and cost effectively repair a paper machine dryer journal moisture barrier. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.
Generally speaking, this invention fulfills these needs by providing a method to repair a moisture barrier separating a paper machine dryer drum from the dryer journal. The air cavity located between the dryer steam intake pipe and the dryer journal is filled with a flowable moisture barrier. The flowable moisture barrier in the cavity seals any leaks in the journal moisture barrier.
The above and other advantages, features and benefits of the present invention will become more apparent by considering the following detailed description and drawings.